From an optimisation perspective using smaller launch vehicles will force some of that optimisation to take into account the size of the launch vehicle and compromises will be made.

A STS HLV along the lines of the above Ares I mentioned could have cargo with diameters of up to 10m and maybe 20m in length. This could transport a huge Bigelow inflatable or possibly an entire fully fuelled Bigelow Nautilus Moon Cruiser in a single lift. The extra time needed to get maybe 4 or 5 delta launches and the in orbit assembly done could mean a delay of a year.

Also the problem gets worse when building large infrastructure such as an orbital assembly yard or a moon base. You could end up with construction times taking over a decade with 30 or 40 launches rather than less than a year. The cost would increase because additional launches would be required for supplies and crew rotations to cover the extended period. The ISS has shown some of the problems associated with relying on small cargo craft like the Soyuz.

A moon base brings additional problems, a heavy lift can deliver a complete base on the moon whereas smaller launcers require in orbit assembly or assembly on the moon moving across the lunar surface. The alternative would be to create a much smaller moon base.

Even the use of ISRU will not help the fact that the initial infrastructure is likely to be smaller and less capable using smaller launchers. Plus there is always the possibility of funding being cut or the project being scaled down if the assembly takes place over a longer period.

EDIT: It seems that Boeing and Lockheed are now working together on selling EELVs to USAF and NASA, true competition in action.

In my last post I tried to optimize somewhere between the size of current spacecrafts and the heavy lifter that would launch the complete vehicle from Earth. My thought allows for heavy lifters but reduces them down from 100 tons.

In principle two heavy lifters would be sufficient - the heavier (80 tons for example) operating from the moon to the Lagrange point and the lighter (20 tons for example) operating from Earth to the Lagrange point. Assembly/docking would take place at the Lagrange point - not in the usually used orbits.

I don't like any one-use-only concepts or one-way-approaches because they are missing possible synergies and economies of scope. In the Bush-plan the moon seems to be the base from which manned Mars missions are to be launched. So any ISRU would not only be use to build the lunar station but the launch site and the launch equipment too. Then this could include ISRU-based vehicle building too - the industry would be there. this industry would be based on new developed technologies which would be higher sophisticated than the earthian ones.

The recently developed rover which can produce solar cells out of lunar dust and install them at the lunar surface can be the first step to such technologies. The NASA wants the CEV to have in 2014 latest - sufficient time to do further developments of that technology. The fly-offs of the CEV-prototypes will take place in 2008 - suficient time too. The solar cells producing rover has been developed in a short time...

If no one-use-only-concepts would be apllied but multiple-use concepts for different purposes some of which can't be predicted then it a part of the 100 tons-vehicle could and should be built at the moon.

It seems by this article that Griffin want's to keep NASA's options open by retaining the shuttle stack (while getting rid of the orbiter) as a heavy lift vehicle. He talks about infrastructure in terms of 100 tons and a CEV of a couple of 10s of tons which might be launched on an EELV, although he did mention that NASA were not required to use one just that it was recommended that they did.

I guess that the size he thinks the CEV will be will be to big to launch on a Falcon V class of vehicle.

I must admit that the more I hear him talk the more I like what he has to say, I hope he gets the political and financial support needed to follow through on his plans.

I have read three articles today about the CEV - including that one you are referring to, Andy Hill.

To me it looks like a modular concept - the modules seem to increase the distance capacity.

What Griffin says seems to have to do with the fact that he knows what the Shutlle stack is capable of, that it is available and there are certain experiences with it - the stack is no experiment. So he sees no reason to give up that certainty. But he seems to consider the cargo bay of the Shuttle to be a waste of weight and volume - which I agree to by far.

But he seems to consider the cargo bay of the Shuttle to be a waste of weight and volume - which I agree to by far.

I think to clarify things, it is not the capacity of the orbiter he objects to it is the fact that you have the weight of the orbiter itself to lift. What he seems to be suggesting is replacing the heavy orbiter with a light weight payload canopy, thereby increasing the payload size and weight that can be carried on the existing shuttle stack. How light the canopy could be made is dependant on whether you wished to keep the download capability from orbit in which case a heatshield and decelleration method will be required.

You could have 2 different canopies to maximise the lifting capacity and use a throw away light weight one when no download was required.

This would still produce a vehicle that could place 70-80 tons (my best guess) into orbit in one go which equates to 5 or 6 Delta Heavy launches.

_________________A journey of a thousand miles begins with a single step.

Only Energiya Buran was truly modular. The Zenit strap-ons were EELV's in thie own right--the Buran orbiter allowed down-lift and a stable platform for cosmonauts to have used--and to return goods from 100 ton segments.

The problem with the idea of multiple smaller launches is that that philosophy is what held the ISS back--20 ton at a time assembly. Energiya could have had it done in five payload only launches.

The modularity of former vehicles is of no relevancy here if this is answer to that post in which I said that the CEV-concept of Lockheed Martin seems to be modular.

What the articles are reporitng about Lockheed's concept and what they quote the lockheed people to have said seems to mean that the winged crew vehilce can fly of it's own if a flight to orbit is to be done. Lockheed sounds as if they have in mind to do so in the fly off - y prototype will be used and the idea is not in focus currently but they have it in mind.

For a flight to the moon the crew vehilce will sit on something that looks like an engine stage or module to my eyes. And for a flight to Mars there will be another engine.

This would mean that the engine for the lunar mission or the engine for the martian mission are NO integral parts of the crew vehicle - they can be added but they don't need to if Moon - or Mars - is not the destination but the orbit.

The concept seems to include replacement of onw engine by another. This is modularity.

Regarding the ISS the mulitole smaller launches have to do with the fact that the modules of the ISS are coming from several countries and agencies. The parts are differnet to each other regarding pruposes and functions - and they were ready at different dates. So there never has been a chance not to do multiple smaller launches.

For this reason the multiple small launches for the ISS are no valid example here - the project doesn't allow for one or a few heavy launches because of organization, property rights and production.

And the issue

Quote:

Large boosters are simply more economical than smaller ones.

is valid under some aspects only but not necessaryly under all aspect, not in general. So it is required to list the aspects explicitly that are applied to conclude this issue.

Multiple launches can have their economies of scale as well as one heavy booster can hyve them. And justifications for smaller launches can be outside the topic of this thread at the company level for example.This is a topic of Economics which should be discussed in the Financial Barriers section but not here.

Modularity, safety, making technological use of the Moon - for that this section is right and correct and on such things the threads should focus here. Which mostly by far is done very well.

Regarding the ISS the mulitole smaller launches have to do with the fact that the modules of the ISS are coming from several countries and agencies. The parts are differnet to each other regarding pruposes and functions - and they were ready at different dates. So there never has been a chance not to do multiple smaller launches.

For this reason the multiple small launches for the ISS are no valid example here - the project doesn't allow for one or a few heavy launches because of organization, property rights and production.

And the reason for these small launches was that there was no HLV available at the time, the ISS had to be designed that way to allow it to get into orbit. As a further point a lot of the individual parts were designed to be shipped only by the shuttle, this is was to take advantage of the shuttle's larger capacity. If a HLV capable of placing 50-100 tons into LEO had been available this would probably have been used instead and components would have been optimised to allow them to be bigger and hence would have been esier to assemble and probably safer due to less joints. This reliance on the shuttle instead of a HLV for the ISS stopped construction when it was grounded. If a HLV had been produced to ferry larger parts then the ISS would have been built now and the shuttle would have been retired in favour of a smaller safer crew craft and not be the drain on finances it has become.

Even now if a HLV existed it might be possible to launch groups of modules to the ISS at a time that were already integrated with each other, making the process quicker. The 28 launches required to finish the ISS could be reduced significantly if this was possible. This highlight the fact that NASA has needed a HLV for sometime and have continually ducked the issue which has lead to problems in the past that could have been avoided, its about time they bit the bullet and built one.

This is why reliance on EELVs to build space structure without a HLV is a mistake and their use for the CEV should be avoided. They could be used to launch smaller crew transports, but the heavy versions are probably to big and costly for this.

_________________A journey of a thousand miles begins with a single step.

the more parts of an object have to integrated to each other that come from different companies and fbriques acroos the world the more the costs of the object formed by thes parts may increase.

It may turn out that currently a heavy lifter is ineconomic. It's correct that a heavy lifter has economies of scale that alighter lifter doesn't have. But these are economies of sclae of weight - what about the economies of scale of the launche site of the heavy lifter?

This is not meant to discuss economics here - that should be done in the Economics-related section(s). It's meant as the question after the launch site technology. Without it the heavy lifter can't be launched and this technology may be a much more costly investment than the launch technolgies for the lighter lifters. In that case the heavy lifter would be more economic only if there are more launches of that heavy lifter than the current number of launches of lighter lifters.

But the volume of the heavy lifter is a factor that works against a larger number of launches.

What improvements or revolutions of llaunch site technologies are required to keep the investment in it close to the level of current launch site technologies?

Another technological point is that if the larger and heavier already integrated portions of the ISS would have been launched more investments would have been required to handle these portions and to prevent damages. The capacities of the production sites to handle larger weights and volumes are limited - may that they would have to be increased. How often would they be required later? Would it be possible to keep the use of the increased capacities at levels of around 90 %? If not then the approach of larger and heavier portions would increase the costs of the ISS.

Again - this is not meant to discuss economical here: It is meant to indicate that mounting and putting together in space may be the cheaper technology - which should be improved urgently in that case. In space the weight wouldn't have be handled - but inertia of masses has to be handled. A good technology for that purpose may reduce costs farther than the technologies required else.

What about such inertia handling technologies? (But there is another thread about such technologies too)

This artical from NewScientist seems to be suggesting that NASA use the Shuttle Stack to launch the CEV, I have some reservations about that and am not sure they have understood what Griffin was saying but here judge for yourself.

Seems like they are a bit behind what is going on as they say that teams will have to redesign their designs as they may not be big enough, but lockheeds stack is 40 Ton and not the 25 ton they refer to.

Ekkehard

The point would be that the modules need not have been intergrated, they could have been combined in to single large modules making them stronger. Overall smaller modules would probably cost more because of mating surfaces, electrical connections, locking mechanisms and air tight seals that would be needed. As for transporting, 60-80 ton units are routinely moved by road, sea and rail (or possibly air if something like an antimov is used).

Infrastructure costs for a STS HLV are likely to be minimal as they would use existing launch facilities. As for manipulating the larger module onto the HLV they manage to move a 100 ton orbiter around at the moment so I dont see that as a problem.

I would have thought that any assembly done on Earth is infinitely more easy and less risky to do than in space.

_________________A journey of a thousand miles begins with a single step.

I am thinking that Boeing and Lockheed heard Griffin make those remarks already, and that's why we have the announcement of the United Launch Alliance. I read somewhere (space.com?) that ULA was going to be patterned after the United Space Alliance (which operates STS), so I'm gonna guess that Griffin got the shirts at the Big Two into a room and said "My bosses ain't givin' me a lot of cash, so I really don't see myself paying a buttload of money for a new BFR when I have one already"

I expect that LockMart felt thier existing CEV design was readily adaptable to that concept so they decided to go to press, while perhaps the guys at Boeing are redrawing their ship in a hurry, but this may give them the opportunity to publish a design that actually has the STS stack in the pictures.

It seems the timescales may now slip a bit from what the above article says. Then again maybe this is what Griffin had in mind when he said he would accelerate the CEV, mabe by using the STS stack he thinks it can be done quicker.

_________________A journey of a thousand miles begins with a single step.

I would have thought that any assembly done on Earth is infinitely more easy and less risky to do than in space.

Anything that is built on Earth is built to withstand the stresses that being on Earth puts on it, not to mention the even more extreme stresses involved in a launch. Anything that is intended to be built in microgravity, however, can be optimized to have a minimum mass (and therefore weight) involved. The only problems are that we do not have 1) a truly man-rated launch-and-return vehicle, thus precluding the existence of any sort of large-scale in-orbit construction and manufacturing, and 2) practically any experience in said large-scale in-orbit construction and manufacturing (or much of anything, for that matter, besides cute little science experiments).

Risk, of course, is another matter entirely. The absolute velocities, of course, are high, while the relative ones are very low. A construction crew would obviously have to be very well-trained.

Agreed by far. I would like to see the private space companies to take the challenge: to develop the required technologies and to train construction crew. But it can't be done now - it can be done after

1. Bigelow's Nautilus is available in orbit and
2. the ASP is won.

It can't be done only - it should be done to enable the private sector to achieve the destinations and goals too NASA is working on today. It would be an alternative approach providing additional chances.